nfs.systemd(7) — Linux manual page


NFS.SYSTEMD(7)      Miscellaneous Information Manual      NFS.SYSTEMD(7)

NAME         top

       nfs.systemd - managing NFS services through systemd.

SYNOPSIS         top


DESCRIPTION         top

       The nfs-utils package provides a suite of systemd unit files
       which allow the various services to be started and managed.
       These unit files ensure that the services are started in the
       correct order, and the prerequisites are active before dependant
       services start.  As there are quite  few unit files, it is not
       immediately obvious how best to achieve certain results.  The
       following subsections attempt to cover the issues that are most
       likely to come up.

       The standard systemd unit files do not provide any easy way to
       pass any command line arguments to daemons so as to configure
       their behavior.  In many case such configuration can be performed
       by making changes to /etc/nfs.conf or other configuration files
       (see nfs.conf(5)).  When that is not convenient, a distribution
       might provide systemd "drop-in" files which replace the
       ExecStart= setting to start the program with different arguments.
       For example a drop-in file systemd/system/nfs-
       mountd.service.d/local.conf containing
              ExecStart= /usr/sbin/rpc.mountd $RPCMOUNTDOPTS
       would cause the nfs-mountd.service unit to run the rpc.mountd
       program using, for arguments, the value given for RPCMOUNTDOPTS
       in /etc/sysconfig/nfs.  This allows for seamless integration with
       existing configuration tools.

   Enabling unit files
       There are three unit files which are designed to be manually
       enabled.  All others are automatically run as required.  The
       three are:
              This should be enabled on any host which ever serves as an
              NFS client.  There is little cost in transparently
              enabling it whenever NFS client software is installed.

              This must be enabled to provide NFS service to clients.
              It starts and configures the required daemons in the
              required order.

              The blkmapd daemon is only required on NFS clients which
              are using pNFS (parallel NFS), and particularly using the
              blocklayout layout protocol.  If you might use this
              particular extension to NFS, the nfs-blkmap.service unit
              should be enabled.

       Several other units which might be considered to be optional,
       such as rpc-gssd.service are careful to only start if the
       required configuration file exists.  rpc-gssd.service will not
       start if the krb5.keytab file does not exist (typically in /etc).

   Restarting NFS services
       Most NFS daemons can be restarted at any time.  They will reload
       any state that they need, and continue servicing requests.  This
       is rarely necessary though.

       When configuration changesare make, it can be hard to know
       exactly which services need to be restarted to ensure that the
       configuration takes effect.  The simplest approach, which is
       often the best, is to restart everything.  To help with this, the
       nfs-utils.service unit is provided.  It declares appropriate
       dependencies with other unit files so that
              systemctl restart nfs-utils
       will restart all NFS daemons that are running.  This will cause
       all configuration changes to take effect except for changes to
       mount options lists in /etc/fstab or /etc/nfsmount.conf.  Mount
       options can only be changed by unmounting and remounting
       filesystem.  This can be a disruptive operation so it should only
       be done when the value justifies the cost.  The command
              umount -a -t nfs; mount -a -t nfs
       should unmount and remount all NFS filesystems.

   Masking unwanted services
       Rarely there may be a desire to prohibit some services from
       running even though there are normally part of a working NFS
       system.  This may be needed to reduce system load to an absolute
       minimum, or to reduce attack surface by not running daemons that
       are not absolutely required.

       Three particular services which this can apply to are rpcbind,
       idmapd, and rpc-gssd.  rpcbind is not part of the nfs-utils
       package, but it used by several NFS services.  However it is not
       needed when only NFSv4 is in use.  If a site will never use NFSv3
       (or NFSv2) and does not want rpcbind to be running, the correct
       approach is to run
              systemctl mask rpcbind
       This will disable rpcbind, and the various NFS services which
       depend on it (and are only needed for NFSv3) will refuse to
       start, without interfering with the operation of NFSv4 services.
       In particular, rpc.statd will not run when rpcbind is masked.

       idmapd is only needed for NFSv4, and even then is not needed when
       the client and server agree to use user-ids rather than user-
       names to identify the owners of files.  If idmapd is not needed
       and not wanted, it can be masked with
              systemctl mask idmapd
       rpc-gssd is assumed to be needed if the krb5.keytab file is
       present.  If a site needs this file present but does not want
       rpc-gssd running, it can be masked with
              systemctl mask rpc-gssd

FILES         top


       Also similar files in /usr/etc and in related conf.d drop-in

SEE ALSO         top

       systemd.unit(5), nfs.conf(5), nfsmount.conf(5).

COLOPHON         top

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